1. Technical Field
The present invention relates to a liquid droplet discharging apparatus which performs multi-pass printing and a liquid droplet discharging method therefor.
2. Related Art
As an example of a liquid droplet discharging apparatus, an ink jet printer is known which performs image recording (printing) by discharging ink droplets toward various recording mediums such as a paper sheet and a film to form a plurality of dots on the recording medium. For example, in a case where the ink jet printer is a serial printer, with respect to the recording medium, the ink jet printer alternately repeats a dot formation operation (pass) which forms dot rows (raster line) lined up in a main scanning direction of the recording medium by discharging ink droplets from a plurality of nozzles while moving (scanning) a head on which the plurality of nozzles are formed in the main scanning direction, and a sub-scanning operation which moves (transports) the recording medium in a sub-scanning direction which intersects with the main scanning direction. Thereby, dots are lined up without gaps in the main scanning direction and the sub-scanning direction of the recording medium, and an image is formed on the recording medium.
For such an ink jet printer, a technique is known in which the quality of a recorded image is improved by an increase in the number of passes. In JP-A-2010-17976, an image formation method is suggested which divides a printing region according to the density of an image to be recorded on the recording medium, and prints the image while changing the number of scans for each portion of the printing region.
In the image formation method of JP-A-2010-17976, there are cases where it is possible to make unevenness inconspicuous by raising the number of passes for a region in which unevenness is conspicuous. However, a pass superimposing method that further improves image quality is not particularly considered. That is, in a case where the number of passes is raised, there is a problem that unevenness may be generated depending on dot formation characteristics in each pass and a superimposing method of each pass (setting method of a region in which each pass is overlapped).